Triple-expanded mechanical pipe coupling derived from a standard fitting

ABSTRACT

A coupling for joining pipe segments together is disclosed. The coupling is derived from a standard fitting and has a housing with a socket and a first expanded region adjacent to the socket, a second expanded region adjacent to the first expanded region and a third expanded region adjacent to the second. A sealing member is positioned in the first expanded region, a retainer is positioned in the second expanded region and a support washer having transversely oriented radial and coaxial flanges is positioned adjacent to the retainer in the third expanded region. A lip turned inwardly on the second expanded region overlaps the radial flange and captures the support washer, retainer and sealing member within the coupling. The retainer has a plurality of radial teeth angularly oriented to engage a pipe and prevent its removal from the coupling.

RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.10/123,607, filed Apr. 16, 2002, now U.S. Pat. No. 6,913,292 which is acontinuation-in-part of U.S. application Ser. No. 10/007,951, filed Dec.3, 2001, which is based on and claims priority of U.S. ProvisionalApplication No. 60/262,820, filed Jan. 19, 2001.

FIELD OF THE INVENTION

This invention relates to couplings for pipes and especially tomechanical couplings derived from standard fittings which effect astrong, reliable joint with a fluid-tight seal without the need forbrazing or soldering.

BACKGROUND OF THE INVENTION

The construction of piping networks requires couplings that can formfluid-tight joints between pipe ends which can withstand externalmechanical forces, as well as internal fluid pressure and reliablymaintain the integrity of the joint. Many forms of joints are known,such as brazed or soldered joints, threaded joints, welded joints andjoints effected by mechanical means.

For example, copper tubing, which is used extensively throughout theworld to provide water service in homes, businesses and industry, istypically joined by means of couplings which are soldered to the pipeends to effect a connection.

The use of copper tubing for piping networks is so widespread thatstandard tubing sizes have been established in various countries. Forexample, in the U.S., there is the ASTM Standard; in Germany, the DINStandard; and in the United Kingdom, the British Standard (BS). Chart 1below shows a portion of the range of outer diameters of the variousstandard copper tubes listed above.

Chart 1 Standard Outer Copper Tube Outer Diameters ASTM DIN BS ½″ 15 mm15 mm ¾″ 22 mm 22 mm 1″ 28 mm 28 mm 1.25″ 35 mm 35 mm 1.5″ 42 mm 42 mm2″ 54 mm 54 mm

Naturally, there are standard pipe fittings such as elbows (45° and90°), tees and straight segments matched for use with the standard tubediameters. These standard fittings are defined in the U.S. by ASMEStandard B16.22a-1998, Addenda to ASME B16.22-1995 entitled “WroughtCopper and Copper Alloy Solder Joint Pressure Fittings” dated 1998. Thestandard fittings have open ends with inner diameters sized to acceptthe outer diameter of a particular standard tube in mating contact foreffecting a soldered joint.

In addition to the standard fittings described above, other components,such as valves, strainers, adapters, flow measurement devices and othercomponents which may be found in a pipe network, will have a couplingwhich is compatible with the standard pipe, and it is understood thatthe term “coupling”, when used herein, is not limited to a standardelbow, tee or other fitting but includes the open end of any componentuseable in a piping network which serves to couple the component to thepipe end.

A soldered joint is effected between a standard diameter tube end andits associated standard fitting by first cleaning the surfaces to bejoined, typically with an abrasive such as a wire brush or steel wool,to remove any contaminants and the oxide layer which forms on thesurfaces. Next, the cleaned surfaces are coated with a flux material,usually an acid flux, which further disrupts the oxide layer (especiallywhen heated) and permits metal to metal contact between the fitting, thepipe end and the solder. The pipe end is next mated with the fittingthereby bringing the cleaned, flux coated surfaces into contact. Thefitting and pipe end are then heated to the melting temperature of thesolder, and the solder is applied to the interface between the tube andthe fitting. The solder melts, flows between the surfaces of the pipeend and the fitting via capillary action and upon cooling andsolidifying forms the solder joint. Excess flux is removed from theouter surfaces to prevent further acid etching of the pipe near thejoint.

While the soldered joint provides a strong, fluid-tight connectionbetween pipe end and fitting, it has several disadvantages. Many stepsare required to make the soldered joint, thus, it is a time consumingand labor intensive operation. Some skill is required to obtain aquality, fluid-tight joint. Furthermore, the solder often contains lead,and the flux, when heated, can give off noxious fumes, thus, exposingthe worker to hazardous substances which can adversely affect healthover time. The joint is typically heated with an open gas flame whichcan pose a fire hazard.

To overcome these disadvantages, many attempts have been made to createmechanical couplings which do not require solder or flame to effect astrong, fluid-tight joint. Such mechanical couplings often use anover-sized opening accommodating an O-ring for sealing purposes and anannular retainer interposed between the outer diameter of the pipe endand the inner diameter of the coupling to mechanically hold the partstogether. The retainer often has radially extending teeth which dig intothe facing surfaces of the coupling and the pipe end to resistextraction of the pipe end from the coupling after engagement.

While these mechanical couplings avoid the above identified problemsassociated with soldered joints, they can suffer from one or more of thefollowing disadvantages. To be effective, the retainer requiressufficient space within the coupling. Thus, the couplings tend to beoversized relatively to the pipes they are intended to receive, and ifexisting standard couplings are to be adapted for use with such amechanical system, it is usually necessary to adapt a larger sizestandard fitting to a smaller size standard pipe. This is more expensivethan adapting the standard fitting appropriate to the standard pipe inwhat is known as a “size-on-size” fitting. For example, a standard ¾inch pipe fitting may be used to couple a ½ inch standard copper pipe ina mechanical system (not “size-on-size”). Furthermore, the retainer maynot provide adequate pull-out strength, and the pipe end could beinadvertently separated from the coupling, for example, during apressure spike within the pipe, caused by a sudden closing of a valve(the “water hammer effect”) which places the joint under tension.

The retainer also does not help keep the pipe end coaxial with thecoupling upon insertion, allowing the pipe end to tip and deform theretainer and gouge the inside surface of the coupling or an elastomericseal, such as an O-ring. In such a mechanical joint, there isfurthermore little or no resistance to axial rotation of the piperelatively to the coupling (i.e., relative rotation of the pipe andcoupling about the longitudinal axis of the pipe). Thus, valves or otheritems mounted on the pipe will tend to rotate. Mechanical joints withretainers also tend to have little resistance to bending, allowing thepipe too much angular free play and permitting the pipe to “walk” out ofthe joint under repeated reversed bending loads. Excessive free playalso tends to disengage the teeth on one side of the retainer and deformthe teeth on the other side, weakening the joint. Furthermore, use of anenlarged section to accommodate the retainer may cause energy lossimpeding fluid flow if the fluid is forced to flow into a couplinghaving a larger cross-sectional area. In general, when mechanicalcouplings are designed to overcome the aforementioned inherentdisadvantages, they tend to suffer from a high part count, making themrelatively complex and expensive.

There is clearly a need for a mechanical pipe coupling which avoids thedisadvantages of both soldered pipe fittings, as well as prior artmechanical fittings described above, and which can be derived fromexisting standard fittings and used with pipes appropriate to thestandard fitting in a “size-on-size” association rather than using alarger size fitting to couple smaller diameter pipes together.

SUMMARY AND OBJECTS OF THE INVENTION

The invention concerns a pipe coupling having a socket with a diametersized according to a standard to receive a pipe end having a diameteralso sized according to the standard to be compatible with the socket.Preferably, the standard is ASME Standard B16.22a-1998, although otherstandards, such as the British Standard and the German DIN standard, arealso contemplated.

The pipe coupling preferably comprises a stop surface positionedadjacent to one end of the socket, the stop surface extending radiallyinwardly and being engageable with the pipe end to prevent the pipe endfrom passing through the pipe coupling. A first expanded region ispositioned adjacent to another end of the socket, the first expandedregion having a larger diameter than the socket and sized to receive asealing member, such as an elastomeric ring positionable therein foreffecting a seal between the pipe coupling and the pipe end. A shoulderis positioned between the socket and the first expanded region, theshoulder being engageable with the sealing member when it is positionedin the first expanded region.

A second expanded region is positioned adjacent to the first expandedregion, the second expanded region preferably having a larger diameterthan the first expanded region and sized to receive a retainerpositionable therein for retaining the pipe end within the pipecoupling. There may be a shoulder positioned between the first andsecond expanded regions. Preferably, the retainer comprises a ring sizedto circumferentially engage the second expanded region (and theshoulder, when present), and a plurality of flexible, resilient,elongated teeth arranged circumferentially around the ring. The teethproject substantially radially inwardly from the ring and are angularlyoriented in a direction away from the opening. The teeth are engageablecircumferentially with the pipe end for preventing movement of the pipeend outwardly from the bore.

A third expanded region is positioned adjacent to the second expandedregion, the third expanded region having a larger diameter than thesecond expanded region. There may be another shoulder positioned betweenthe second and third expanded regions. The third expanded region formsan open end of the pipe coupling housing for receiving the pipe end. Thethird expanded region is sized to receive a support washer therein forsupporting the pipe end. The support washer has a radially inwardlyfacing surface having a diameter substantially equal to and coaxial withthe socket diameter for circumferentially engaging and supporting thepipe end. The two-point support provided by the socket and the supportwasher provides substantial resistance to bending of the pipe within thecoupling. The support washer preferably has a circumferential collarwhich engages and supports the retainer.

A lip is positioned at the open end formed by the third expanded region,the lip extending substantially radially inwardly to be engageable withthe support washer when it is positioned in the third expanded region.The various shoulders and the lip capture the sealing member, theretainer, and the support washer between one another. The lip may alsobe biased toward the socket so as to forcibly engage the support washerand clamp the washer within the third expanded region.

The invention also concerns a method of manufacturing a pipe couplinghousing and a pipe coupling for receiving a pipe end. The method ofmaking the housing comprises the steps of:

(A) providing a fitting having a socket;

(B) expanding a portion of the socket into a first expanded regionhaving a larger inner diameter than the socket;

(C) expanding a portion of the first expanded region into a secondexpanded region having a larger inner diameter than the first expandedregion; and

(D) expanding a portion of the second expanded region into a thirdexpanded region having a larger inner diameter than the first expandedregion, the third expanded region forming an open end for receiving thepipe end.

The following steps use the coupling housing to form the coupling:

(E) positioning a sealing member preferably within the first expandedregion;

(F) positioning a retainer preferably within the second expanded region;

(G) positioning a support washer preferably within the third expandedregion; and

(H) forming a lip extending substantially radially inwardly at the openend to capture the sealing member, the retainer and the support washerwithin the expanded regions.

Preferably, the socket is sized according to a standard.

It is an object of the invention to provide a mechanical pipe couplingwhich does not need to be soldered, brazed, welded, threaded oradhesively bonded to effect a joint.

It is another object of the invention to provide a standard mechanicalpipe coupling which can be derived from existing standard pipe fittings.

It is still another object of the invention to provide a standardmechanical pipe coupling which can be used in a “size-on-size”association with an appropriate standard pipe for increased economy,improved fluid flow and compactness.

It is again another object of the invention to provide a standardmechanical pipe coupling which has substantial resistance to bendingpreventing excessive free play between pipe and coupling.

It is yet another object of the invention to provide a standardmechanical pipe coupling providing substantial resistance to axialrotation to inhibit rotation of valves and other components about thelongitudinal axis of the pipe.

These and other objects and advantages of the invention will becomeapparent upon consideration of the following drawings and detaileddescription of preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal sectional view of a pipe couplinghousing according to the invention;

FIG. 1A is a partial longitudinal sectional view of an alternateembodiment of a pipe coupling housing according to the invention;

FIG. 2 is a longitudinal sectional view of a pipe coupling according tothe invention;

FIG. 3 is a front perspective view of a retainer according to theinvention;

FIG. 4 is a rear perspective view of the retainer shown in FIG. 3;

FIG. 5 is an exploded perspective view of a pipe coupling in the form ofan elbow fitting according to the invention; and

FIGS. 6 through 9 are partial longitudinal sectional views of variousdifferent embodiments of the coupling according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a pipe coupling housing 10 according to the inventionhaving a socket 12 with an inner diameter 14 sized according to astandard to receive a pipe end sized, according to a compatiblestandard, to interfit within the socket 12. Preferably, coupling housing10 is a modification of an existing standard pipe fitting, for example,an ASME Standard pipe fitting according to Standard number B16.22a-1998for wrought copper and copper alloy solder joint pressure fittings.Fittings meeting the specification of other standards, such as theGerman DIN standard and the British BS standard, may also be modified toderive the coupling housing 10.

A stop surface 16 is positioned adjacent to one end 18 of the socket 12.Stop surface 16 extends radially inwardly and is, thus, engageable withan end of a pipe received within the socket to prevent the pipe end frompassing through the coupling housing. Stop surface 16 iscircumferentially continuous around housing 10, but may also bediscontinuous as shown by stop surface 16 a in FIG. 1A.

A first expanded region 20 is positioned at the other end 22 of thesocket 12, the first expanded region having a larger inner diameter 24than the socket inner diameter 14. A shoulder 25 is positioned betweenthe socket 12 and the first expanded region 20. The diameter 24 of thefirst expanded region is sized to receive a sealing member, the sealingmember being engageable with the shoulder as described below.

A second expanded region 26 is positioned adjacent to the first expandedregion 20. The second expanded region 26 has a larger inner diameter 28than the inner diameter 24 of the first expanded region 20 and is sizedto receive a retainer, also described below. A shoulder 27 is preferablypositioned between the first and second expanded regions for engagingthe retainer.

A third expanded region 29 is positioned adjacent to the second expandedregion 26. The third expanded region 29 has a larger diameter 31 thanthe second expanded region and is sized to receive a support washertherein for supporting a pipe end as described below. Preferably ashoulder 33 is positioned between the second and third expanded regions,the shoulder 33 for engaging the support washer. The third expandedregion 29 forms an open end 30 of the pipe coupling housing 10 forreceiving the pipe end.

A lip 32 is positioned at the open end 30. The lip 32 extends radiallyinwardly from the third expanded region 29 and is engageable with theaforementioned support washer to capture and hold the support washer,retainer and sealing member within the coupling housing 10. The lip 32may be biased toward socket 12 to forcibly engage the support washer andclamp it against the shoulder 33 within the third expanded regionindependently of the other components, such as the retainer and thesealing member.

Preferably, pipe coupling housing 10 is derived by die forming thesocket of an existing standard pipe fitting to create the expandedregions 20, 26 and 29, the lip 32 being turned inwardly in a lateroperation after internal components such as the aforementioned sealingmember, retainer and support washer are inserted into the couplinghousing 10 to form a coupling according to the invention described indetail below.

While any standard fitting may be used as a starting point, theinvention is particularly advantageously used with the ASME standardfittings compatible with copper tubing having a nominal diameter between½ and 2 inches. Similarly, the German and British standard fittings forcopper tubing between 15 mm and 54 mm are also favored. It is understoodthat the invention is not limited for use with copper tube and could beapplied to plastic or steel pipes and fittings for example. While it isadvantageous to begin with a standard fitting from an economicstandpoint, the coupling housing 10 could also be custom made for aparticular application.

FIG. 2 shows a pipe coupling 40 according to the invention assembledfrom its various components including pipe coupling housing 10, asealing member 42, a retainer 44 and a support washer 45. A pipe end 46is shown in phantom line received within the coupling 40. Pipe end 46 ispreferably a standard pipe, compatible with ASME Standard B16.22a-1998,for example, and the coupling housing 10 is preferably formed from afitting originally designed according to the same standard to receivethe pipe end 46 and modified by the formation of the expanded regions20, 26 and 29 and the lip 32.

To realize economic advantage, it is preferable to modify a standardfitting intended originally for use with the diameter of the pipe end 46and achieve a “size-on-size” relationship between the coupling and thepipe end. Size-on-size refers to the fact that the fitting beingmodified is for the size of pipe being coupled and not a fittingintended for a larger sized pipe which is then modified into a couplingwhich can take a smaller sized pipe.

As shown in FIG. 2, the inner diameter 14 of socket 12 is sized toreceive and support the pipe end 46. Stop surface 16 engages pipe end toposition it properly within coupling 40 and prevent it from passingthrough the coupling housing 10.

Sealing member 42, positioned adjacent to socket 12, is preferably anelastomeric ring having an angularly oriented circumferential surface 47sloping toward the open end 30 of the coupling housing 10. Slopingsurface 47 acts as a lead-in and helps prevent the sealing member frombeing pinched between the pipe end and shoulder 25. The sloping surface47 also acts as a guide to align the pipe end 46 with the socket 12 andthus helps protect the seal from insertion damage due to misalignmentbetween the pipe end 46 and the coupling 40. The sloping surface 47 alsocauses a reduction in the insertion force required to seat a pipe end 46into the coupling 40. Sealing member 42 may also be an O-ring as shownin FIG. 6, or any other type of sealing member which will effect afluid-tight joint between the pipe end and the coupling.

A fluid-tight seal is effected between the coupling housing 10 and thepipe end 46 by compressing the sealing member 42 in the annular space 48between the outer surface 50 of pipe end 46 and the inside surface 52 ofthe first expanded region 20. Sealing member 42 seats against shoulder25 which prevents it from moving deeper into the coupling housing 10when pipe end 46 is inserted through opening 30 to engage the sealingmember and be received in socket 12.

Retainer 44 is shown in detail in FIGS. 3 and 4 and comprises a ring 54sized to engage the second expanded region 26 of coupling housing 10(see FIG. 2). The ring seats within region 26 and stabilizes theretainer within the coupling housing. Preferably, coupling housing 10has the second shoulder 27 which engages the ring 54 to properlyposition retainer 44 and prevent it from moving deeper into the couplinghousing 10. In the absence of shoulder 27, the retainer 44 seats againstthe sealing member 42. Retainer 44 may also seat against an intermediatecomponent as shown in FIG. 6 and described below.

Retainer 44 has a plurality of flexible, resilient teeth 60 which arearranged circumferentially around the ring 54 and extend substantiallyradially inwardly thereof. Teeth 60 are angularly oriented in adirection away from opening 30 (see FIG. 2) and are resiliently biasedto engage outer surface 50 of pipe end 46. The angular orientation ofteeth 60 allows the pipe end 46 to be received within opening 30 andpass through the retainer 44 and the sealing member 42 into socket 12and seat against stop surface 16 but prevent withdrawal of the pipe end46 outwardly from the coupling. Outward motion of the pipe end will tendto simultaneously compress and rotate the teeth inwardly thereby causingthem to dig into the pipe outer surface 50 and retain the pipe withinthe coupling in a self-jamming manner such that, as greater force isapplied to withdraw the pipe from the coupling the teeth 60 dig furtherand exert proportionally greater force to resist the outward motionuntil they bend or buckle.

As shown in FIGS. 3 and 4, ring 54 may have projections 58 extendingradially outwardly. Projections 58 engage the second expanded region 26and inhibit relative rotation between the retainer 44 and the couplinghousing 10. Teeth 60 are biased forcibly against the outer surface 50and dig into this surface to inhibit relative rotation between the pipeend 46 and the retainer 44. Together, the teeth 60 and the projections58 inhibit relative rotation between the pipe end 46 and the couplinghousing 10. Thus, valves or other items mounted on plain end pipe (i.e.,pipe ends having no grooves or other modifications) by means of thecoupling 40 will be less likely to rotate into an inconvenient orinaccessible position where they become difficult or impossible toactuate or service.

Preferred materials for the retainer include stainless steel to preventcorrosion, beryllium-copper alloys for excellent flexibility andstrength and galvanic compatibility, as well as other resilient,flexible metals. Engineering plastics are also feasible.

Support washer 45, best shown in FIG. 2, preferably comprises a radiallyoriented circumferential flange 62 and a collar 64, alsocircumferential, but oriented transversely to the radial flange 62.Thus, support washer 45 has an “L”-shaped cross-section as shown whichprovides excellent torsional stiffness for support of the pipe end asdescribed below. Radial flange 62 is in overlapping relation with andengaged by the lip 32 and thereby retained within the third expandedregion 29. Preferably, the collar 64 extends inwardly of the pipecoupling housing 40 to support the teeth 60 against excessivedeflection. By continuously supporting the teeth circumferentiallyaround the coupling, the pull-out force required to remove the pipe end46 from the coupling is increased because the teeth 60, when supportedby the collar 64, will bend or buckle at a significantly higher loadthan when unsupported. The third expanded region 29 helps preventrotational deflection of the support washer 45 when the lip 32 is turnedinwardly to capture the washer 45, retainer 44 and sealing member 42within the coupling. With significant rotation of the support washer 45prevented, the collar 64 does not impinge on and deflect the teeth 60radially outwardly away from the pipe end outer surface 50. If suchoutward radial deflection of teeth 60 were permitted it would reduce theeffectiveness of the retainer at holding the pipe end within thecoupling housing 10. The teeth 60 must be biased against the surface 50to effectively engage and jam against the pipe end 46.

The collar 64 forms an inwardly facing surface 66 having an innerdiameter 68 substantially equal to and coaxial with the inner diameter14 of the socket 12. Together, the socket 12 and surface 66 engage andsupport the pipe end 46 when it is inserted into the coupling housing,the surface 66 and socket 12 providing a “two-point” support over asubstantial length of the coupling housing. This two-point supportafforded by the surface 66 and socket 12 provides substantial resistanceto bending of the pipe end 46 within the coupling housing 10 and reducesfree play of the pipe end. Increased bending stiffness and reduced freeplay help to ensure a reliable fluid-tight joint between the coupling 40and the pipe end 46 which will not leak or come apart under repeatedbending loads. Furthermore, the increased joint stiffness allows thesame hanger spacing for mounting the pipe as used in a soldered jointsystem.

Preferred materials for the support washer include stainless steel toprevent corrosion and beryllium-copper alloys, as well as high strengthengineering plastics.

FIG. 5 shows an elbow fitting 70 comprising a pipe coupling 40 accordingto the invention. As noted above, in addition to the straight throughand elbow type couplings illustrated, any type fitting, such as a teefitting, a fitting forming part of a valve, a sprinkler head, a filteror any other mechanical component, may be adapted to use a couplingaccording to the invention.

FIG. 5 presents an exploded view which is useful to describe how acoupling according to the invention is manufactured and used.Preferably, elbow fitting 70 begins as a standard fitting, for example,a standard ASME wrought copper or copper alloy solder joint pressurefitting according to ASME Standard B16.22a-1998 having a socket 12 sizedto receive pipe end 46. Portions of the socket 12 are expanded,preferably by die-forming, into first, second, and third expandedregions 20, 26 and 29. Shoulders 25, 27 and 33 are preferably formed inthe process of expanding the original socket 12. Next, sealing member 42is positioned within the first expanded region 20, engaging shoulder 25.Retainer 44 is then positioned adjacent to the sealing member 42 in thesecond expanded region 26, engaging shoulder 27. Support washer 45 isnext positioned in the third expanded region 29 adjacent to retainer 44with collar 64 facing inwardly towards socket 12 for supporting teeth 60on retainer 44 against excessive deflection. After the components areinserted and properly seated within the expanded regions, the lip 32,shown in phantom line, is formed by turning a portion of the secondexpanded region 26 radially inwardly to engage radial flange 62 ofsupport washer 45 and capture the support washer, the retainer 44 andthe sealing member 42 within the coupling 40. The lip 32 may be biasedtoward the socket 12 so as to forcibly engage and clamp the internalcomponents in place. Lip 32 also forms opening 30 for receiving pipe end46.

Coupling 40 thus formed is ready to receive a pipe end 46 in sealingengagement. Pipe end 46 may have a groove 72 cut or cold-formed in itsouter surface 50 to engage teeth 60 of retainer 44 and provideadditional gripping force preventing inadvertent separation of the pipeend from the fitting 70. The groove 72 may have knurling 74 or beotherwise textured to engage teeth 60 and prevent or at least inhibitrotation of the pipe end relative to the retainer. As described above,retainer 44 may have projections 58 extending outwardly from its ring 54to engage the second expanded region 26 and prevent or inhibit rotationof the retainer 44 relative to the coupling 40. Together, knurling 74,teeth 60 and projections 58 help inhibit rotation of the pipe end 46about its long axis 76 relative to the fitting 70. Thus, valves or otheritems mounted on the pipe by ,means of the coupling 40 will be lesslikely to rotate into an inconvenient or inaccessible position wherethey become difficult or impossible to actuate or service.

An additional groove 78 may also be formed in the pipe end 46 in spacedrelation to the groove 72. The groove spacing is designed such thatgroove 78 aligns with flange 62 when the pipe end 46 is inserted intothe coupling 40 to a depth sufficient for teeth 60 on retainer 44 toengage groove 72. Groove 78, thus, provides a visual indicator whichallows the technician installing the pipe to immediately verify that thepipe end 46 is properly engaged with the coupling 40 to form afluid-tight joint.

Plain end pipe (i.e., pipe ends having no grooves 72 or othermodifications to increase pull-out strength) may also have a groove 78or other form of witness mark, such as a score line, printed indicia andthe like, which is positioned in spaced relation to the end of the pipesuch that, when the witness mark aligns with flange 62 the pipe end 46is substantially seated against the stop surface 16. The witness markprovides visual confirmation that the pipe end is properly and fullyengaged with the coupling.

FIGS. 6–9 illustrate alternate embodiments of the pipe couplingaccording to the invention. In FIG. 6, coupling housing 10 has a sealingmember 42 formed by an O-ring 80 positioned within the first expandedregion 20. A washer 82 is positioned adjacent to the O-ring and retainer44 is adjacent to the flat washer 82 in the second expanded region 26.Support washer 45 is positioned in the third expanded region 29 and hascollar 64 for support of teeth 60 on the retainer 44. Lip 32 is inoverlapping relation with radial flange 62 to capture the componentswithin the coupling housing 10. Washer 82 separates and supports boththe O-ring 80 and the retainer 44, allowing a relatively simple retainerdesign to be used which has only a ring 54 supporting teeth 60, thus,avoiding the need for a back flange on the retainer for engaging theO-ring.

FIG. 7 shows an embodiment of a coupling 40 wherein the collar 64 of thesupport washer 45 extends outwardly from the coupling housing 10 ratherthan inwardly toward the socket 12. This configuration provides theadvantage of extending the length over which the coupling engages thepipe end, thus, further increasing the bending stiffness of the joint.

FIG. 8 shows a coupling 40 having a support washer 45 with a T-shapedcross section wherein the collar 64 extends both inwardly and outwardlyfrom the housing 10. The extended collar of this embodiment providesboth the increased bending stiffness of the embodiment of FIG. 7, aswell as the support for teeth 60 of retainer 44, thereby providinghigher pull-out loads for the pipe end.

FIG. 9 shows an embodiment of coupling 40 wherein the support washer 45comprises a simple flat washer, the inner diameter 84 of the washerforming the inwardly facing surface 66 for support of the pipe end 46 asdescribed above. Lip 32 engages the support washer 45 to capture andretain the other components such as the retainer 44 and the sealingmember 42 within the coupling housing 10.

Couplings according to the invention provide a mechanical pipe couplingwhich can form a reliable fluid-tight joint without the hazardsassociated with brazing, welding or soldering while taking advantage ofexisting standard fittings in a size-on-size relationship with standardpipe to achieve significant economical advantage.

1. A pipe coupling sealingly engageable with a pipe end, said pipecoupling comprising: a coupling housing having a socket with a diametersized to receive and circumferentially support said pipe end; a firstexpanded region positioned adjacent to one end of said socket, saidfirst expanded region having a larger diameter than said socket; a firstshoulder positioned between said socket and said first expanded region;a sealing member positioned in said first expanded region to effect aseal between said pipe coupling and said pipe end, said sealing memberbeing engaged with said shoulder; a second expanded region positionedadjacent to said first expanded region, said second expanded regionhaving a larger diameter than said first expanded region; a retainerinterfitting within said second expanded region, said retainercomprising a ring sized to circumferentially engage said second expandedregion and a plurality of flexible, resilient, elongated teeth arrangedcircumferentially around said ring, said teeth projecting substantiallyradially inwardly from said ring and being angularly oriented towardsaid socket, said teeth being engageable circumferentially with saidpipe end for retaining said pipe end within said pipe coupling; a thirdexpanded region positioned adjacent to said second expanded region, saidthird expanded region having a larger diameter than said second expandedregion and forming an open end of said coupling housing for receivingsaid pipe end; a support washer interfitting within said third expandedregion between said retainer and said open end of said coupling housing;and a lip attached to said coupling housing and positioned at said openend, said lip extending substantially radially inwardly and overlappingand engaging said support washer to capture said support washer, saidretainer and said sealing member between said shoulder and said lip. 2.A pipe coupling housing according to claim 1, wherein said lip is biasedtoward said socket for forcibly engaging said support washer.
 3. A pipecoupling housing according to claim 2, further comprising a secondshoulder positioned between said first and said second expanded regions,said retainer and said support washer being captured between said lipand said second shoulder.
 4. A pipe coupling housing according to claim2, further comprising a third shoulder being positioned between saidsecond and said third expanded regions, said support washer beingclamped between said lip and said third shoulder.
 5. A pipe couplinghousing according to claim 1, wherein said lip extends circumferentiallyaround said open end.
 6. A pipe coupling according to claim 1, whereinsaid support washer has a radially inwardly facing surface having adiameter substantially equal to said socket diameter and coaxialtherewith, said inwardly facing surface being circumferentiallyengageable with said pipe end upon insertion of said pipe end into saidpipe coupling, said pipe end being supportable by said socket and saidinwardly facing surface of said support washer.
 7. A pipe couplingaccording to claim 6, wherein said support washer comprises acircumferential flange and a circumferential collar arrangedtransversely to said circumferential flange, said circumferential flangebeing oriented substantially radially and in overlapping engagement withsaid lip, said circumferential collar being substantially coaxial withsaid socket and forming said inwardly facing surface for supporting saidpipe end.
 8. A pipe coupling according to claim 7, wherein saidcircumferential collar extends outwardly from said open end of saidcoupling housing.
 9. A pipe coupling according to claim 7, wherein saidcircumferential collar extends inwardly of said pipe coupling towardsaid retainer for providing support thereto.
 10. A pipe couplingaccording to claim 7, further comprising a circumferential collaroriented transversely to said circumferential flange and extendingoutwardly from said open end of said coupling housing.
 11. A pipecoupling according to claim 1, further comprising a stop surfacepositioned adjacent to another end of said socket opposite said one end,said stop surface extending radially inwardly and being engageable withsaid pipe end to prevent said pipe end from passing through saidcoupling housing.
 12. A pipe coupling according to claim 1 compatiblewith copper tubing having a nominal diameter between ½ inch and 2 inchesinclusive.
 13. A pipe coupling according to claim 1, wherein saidcoupling comprises an elbow fitting.
 14. A pipe coupling according toclaim 1, wherein said coupling comprises a straight fitting.
 15. A pipecoupling according to claim 1, wherein said support washer comprises acircumferential flange and a circumferential collar arrangedtransversely to said circumferential flange, said circumferential flangebeing oriented substantially radially and in overlapping engagement withsaid lip, said circumferential collar being substantially coaxial withsaid socket and extending inwardly of said pipe coupling toward saidretainer, said circumferential collar for providing support to saidteeth.
 16. A pipe coupling according to claim 1, wherein said teeth havea predetermined length so as to interfit within a groove formedcircumferentially around said pipe end when said pipe end engages saidsocket, said teeth being engageable with said groove to increaseresistance to movement of said pipe outwardly from said coupling.
 17. Apipe coupling sealingly engageable with a pipe end, said pipe couplingcomprising: a coupling housing having a socket with a diameter sized toreceive and circumferentially support said pipe end; a first expandedregion positioned adjacent to one end of said socket, said firstexpanded region having a larger diameter than said socket; a firstshoulder positioned between said socket and said first expanded region;a sealing member positioned in said first expanded region to effect aseal between said pipe coupling and said pipe end, said sealing memberbeing engaged with said shoulder; a second expanded region positionedadjacent to said first expanded region, said second expanded regionhaving a larger diameter than said first expanded region; a retainerinterfitting within said second expanded region and being engageablecircumferentially with said pipe end for retaining said pipe end withinsaid pipe coupling; a third expanded region positioned adjacent to saidsecond expanded region, said third expanded region having a largerdiameter than said second expanded region and forming an open end ofsaid coupling housing for receiving said pipe end; a support washerinterfitting within said third expanded region between said retainer andsaid open end of said coupling housing, said support washer having aradially inwardly facing surface having a diameter substantially equalto said socket diameter and coaxial therewith, said inwardly facingsurface being circumferentially engageable with said pipe end uponinsertion of said pipe end into said pipe coupling, said pipe end beingsupportable by said socket and said inwardly facing surface of saidsupport washer, said support washer comprising a circumferential flangeand a circumferential collar arranged transversely to saidcircumferential flange, said circumferential flange being orientedsubstantially radially, said circumferential collar being substantiallycoaxial with said socket and forming said inwardly facing surface forsupporting said pipe end, said circumferential collar extending inwardlyof said pipe coupling toward said retainer for providing supportthereto; and a lip attached to said coupling housing and positioned atsaid open end, said lip extending substantially radially inwardly andoverlapping and engaging said circumferential flange to capture saidsupport washer, said retainer and said sealing member between saidshoulder and said lip.